JPH0832505A - Signal arrival time correction method in mobile communication system - Google Patents

Abstract

PURPOSE:To enhance the utilizing efficiency of a frequency resource by allowing a mobile station to extract an error signal from a received transmission signal from a base station and adjusting a transmission start timing as to a prescribed time slot in response to the extracted error signal. CONSTITUTION:A CPU 19 of a mobile station discriminates whether or not an error information signal T read from slot data of a communication channel is changed from error information in preceding slot data. When the error information signal T is changed, a slot data transmission start advanced amount at present is maintained. However, when the error information signal T is not changed, whether or not the signal T is logical 1 is discriminated. In the case of T=1, a preset value of a down-counter 41 is decremented by one in order to increase the slot data transmission start advanced amount. Then a time when the count of the counter 41 reaches 0 is decreased, resulting that a DSP 11 controls a transmission section 4 in response to a quickened output of slot data. On the other hand, in the case of T=0, the DSP 11 controls a transmission section 4 with an output delayed by one bit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to TDMA (Time Divis).
The present invention relates to a signal arrival time correction method in a mobile communication system using an ion multiple access (time division multiple access) method.

[0002]

2. Description of the Related Art In a mobile communication system such as MCA (Multi Carrier Access) land mobile communication, a mobile station existing in a service area covered by a base station can perform wireless communication through the base station. It has become. In the case of a so-called large cell service area, the radius is as wide as 30 km, and the propagation time of the transmission signal from the mobile station to the base station varies depending on the location of the mobile station. Therefore, in the TDMA mobile communication system, since the time slot to be transmitted is assigned to each mobile station, the reference start time of each time slot in the base station and the arrival time of the transmission signal from each mobile station are equal. I will not do it. Therefore, in a conventional mobile communication system, a long guard time is provided between each time slot, or a very complicated synchronization circuit is used to absorb a difference in arrival time due to a propagation time of a transmission signal. It was

[0003]

However, providing a long guard time between each time slot reduces the efficiency of utilization of frequency resources, and using a very complicated synchronizing circuit increases the price of the wireless device. There was a problem of becoming a cause. Therefore, an object of the present invention is to realize matching of the reference start time of each time slot in the base station with the arrival time of the transmission signal from each mobile station at a low price and without deteriorating the utilization efficiency of frequency resources. It is to provide a method for correcting a signal arrival time in a mobile communication system capable of performing the same.

[0004]

A signal arrival time correction method in a mobile communication system according to the present invention is a mobile communication system using a time division multiplexing connection system in which a mobile station and a base station wirelessly communicate with each other in a predetermined time slot. In the signal arrival time correction method for correcting the arrival time at the base station of the transmission signal for the predetermined time slot transmitted from the mobile station, the base station receives the transmission signal from the mobile station in the communication channel every time. A delay amount N of the arrival time of the transmission signal from a reference start time of a predetermined time slot is measured, an error information signal T corresponding to the measured delay amount N is included in the transmission signal, and the transmission signal is transmitted to the mobile station. The station extracts the error information signal T from the received transmission signals from the base station, and transmits a predetermined time slot according to the extracted error information signal T. It is characterized by adjusting the start timing.

[0005]

Embodiments of the present invention will now be described in detail with reference to the drawings. In the TDMA wireless apparatus using the signal arrival time correction method of the present invention shown in FIG. 1, the antenna 1 is a transmitting / receiving antenna, and a TDD (Time Divis).
ion Duplex) method is adopted. The receiving unit 3 and the transmitting unit 4 are connected to the terminals of the antenna 1 via the antenna switch 2.
Connected to either one of. The selection of the antenna switch 2 on the receiving unit 3 side is in a steady state. In the receiving unit 3, the high frequency signal which is the received signal from the antenna switch 2 is band-limited by the band limiting filter (BPF) 5 and then supplied to the high frequency amplifier 6. High frequency amplifier 6
The signal amplified by is supplied to the down converter 8 via the band limiting filter 7. Down converter 8
Generates an intermediate frequency signal by mixing the supplied high frequency signal with a local oscillation signal from the VCO 9. The intermediate frequency signal output from the down converter 8 is an A / D converter 10
After being digitized by, it is supplied to a DSP (digital signal processor) 11. The DSP 11 detects the supplied digitized intermediate frequency signal, demodulates an information signal such as a voice signal and a control signal included in the received signal, and supplies the demodulated information signal to the channel coding logic circuit 12. Also, D
The SP 11 performs a modulation operation according to the data signal which is the digital information signal to be transmitted supplied from the channel coding logic circuit 12 and supplies the modulation result to the transmission unit 4.

In the transmitter 4, the digital signal output from the DSP 11 is supplied to the up converter 14 via the D / A converter 13. Upconverter 14
Mixes the modulated signal with the oscillation signal from the VCO 15 and frequency-converts it to a frequency to be transmitted. The oscillation signal is amplified by the front stage amplifier 16 and further amplified by the power amplifier 17 to become a transmission signal. This transmission signal is supplied to the antenna 1 via the antenna switch 2.

The modulation and demodulation operations of the DSP 11 are CPU
It is controlled by (central processing unit) 19. The switching operation of the antenna switch 2, the oscillation frequencies of the VCOs 9 and 15 and the amplification operation of the power amplifier 17 are controlled by the operating state of the DSP 11. The CPU 19 controls the DSP 11 according to the operation from the keyboard 20 and also controls the operation modes of the channel coding logic circuit 12 and the voice CODEC (codec) 21. The channel coding logic circuit 12 operates as a coder for performing a predetermined code conversion on the digital voice signal supplied from the voice CODEC 21 or the digital data signal supplied from the data input / output interface 22.
The code-converted signal is supplied to the DSP 11. Also, DS
An operation as a decoder for decoding the demodulated digital signal supplied from P11 is performed and the decoded digital signal is supplied to the voice CODEC 21 or the data input / output interface 22. Voice CODEC21
Converts the analog audio signal from the microphone amplifier 23 into a digital audio signal of a predetermined format, converts the decoded digital audio signal from the channel coding logic circuit 12 into an analog signal, and supplies it to the speaker amplifier 24. A microphone 25 is connected to the microphone amplifier 23, and a speaker 26 is connected to the speaker amplifier 24.

The data to be transmitted is first supplied from the CPU 19 to the channel coding logic circuit 12 and the voice C
The data is converted into the above data format together with the communication data from the ODEC 21 or the data input / output interface 22, and then supplied to the DSP 11. Communication data is not included until the link is established. The DSP 11 performs data conversion on the supplied data signal by a modulation operation, and D
It is supplied to the / A converter 13. The data signal analogized by the D / A converter 13 is superimposed on the oscillation signal from the VCO 15 by the up converter 14. The oscillation signal including the data signal is amplified by the pre-stage amplifier 16 and further amplified by the power amplifier 17 to be a transmission signal, which is supplied to the antenna 1 via the antenna switch 2. On the other hand, the signal received by the antenna 1 is supplied to the down converter 8 via the antenna switch 2, the band limiting filter 5, the high frequency amplifier 6 and the band limiting filter 7.
The down converter 8 mixes the supplied signal with the local oscillation signal from the VCO 9 to form an intermediate frequency signal, which is digitized by the A / D converter 10 and then the DS signal.
It is supplied to P11. The signal demodulated by the DSP 11 is supplied to the channel coding logic circuit 12. The channel coding logic circuit 12 sends the control data to the CPU 19
And the communication data to the voice CODEC 21 or the data input / output interface 22. That is, if the communication data is voice data, it is voice CODEC2.
1 and is supplied to the data input / output interface 22 if it is not audio data.

The radio equipment having such a configuration is used in both the base station and the mobile station, and in the radio equipment of the base station,
The channel coding logic circuit 12 comprises a delay amount measuring circuit. The delay amount measuring circuit is provided with a shift register 31 to which a data signal from the DSP 11 is supplied, as shown in FIG. Shift register 3
1 shifts while holding data for n bits in synchronization with a clock pulse generated from a means (not shown), and the held output for n bits is supplied to the digital comparison circuit 32. A memory 33 in which a predetermined unique word is stored in advance is connected to the digital comparison circuit 32, and the comparison circuit 32 synchronizes with a clock pulse and holds the output data of the shift register 31 and the predetermined unique word stored in the memory 33. The words are compared and a match pulse is generated for counter 34 when they match. Counter 34
When the slot start pulse indicating the start of one slot is supplied, the clock pulse counts the clock pulse from the initial value, and outputs the count value when the coincidence pulse is supplied.

In the radio equipment of the mobile station, the channel coding logic circuit 12 comprises a time slot format generating circuit and a T value judging circuit. The time slot format generation circuit adjusts the generation timing of the data in one slot to be transmitted (hereinafter referred to as slot data), and the T value determination circuit adjusts the error information T included in the transmission data of the communication channel from the base station. Detect the value of. The error information T is a 1-bit data signal indicating a change in the delay amount N.

The time slot format generating circuit is provided with a bit down counter 41 as shown in FIG. 3, and the bit down counter 41 counts down from an initial value preset by a preset pulse in synchronization with a clock pulse. . This initial value is preset by the CPU 19 according to the delay amount N. The down counting is started in response to the shift start pulse supplied from the CPU 19. The shift start pulse is generated M bits earlier than the slot start pulse (a pulse for starting slot data output when the error is not taken into consideration). Bit down counter 41
Generates a high level output when the count value becomes 0 due to the down counting. AND to the output of the bit down counter 41
The circuit 42 is connected. The AND circuit 42 takes the logical product of the output signal of the bit down counter 41 and the clock pulse. When the delay amount N is 0, the down counter 4
Since M is preset to 1, the clock pulse is generated from the AND circuit 42 when the slot start pulse is generated.

A preset shift register 43 is connected to the output of the AND circuit 42. The shift register 43 receives input data from the voice CODEC 21 or the data input / output interface 22, and presets predetermined transmission format data such as a unique word stored in advance in the transmission data buffer memory 44 according to a preset pulse, and an AND circuit. The data is shifted bit by bit in accordance with the clock pulse from 42 and is output to the DSP 11 as slot data to be transmitted.

On the other hand, in the T value judging circuit, as shown in FIG. 4, the data signal from the DSP 11 is supplied to the comparing circuit 51. The comparison circuit 51 includes 1 of each bit of data.
A reference voltage serving as a threshold for determining 0 is supplied, and the comparison circuit 51 compares the supplied data signal with the reference voltage. The D-type flip-flop 5 is provided at the output of the comparison circuit 51.
2 is connected. The flip-flop 52 is the CPU 1
The output level of the comparison circuit 51 when the T value detection trigger pulse is supplied from 9 is held as the T value and output to the CPU 19. The T value detection trigger pulse is generated at that time because the bit position of the error information T can be known from the synchronization preamble and the unique word in the received data signal.

In the communication system using the wireless device having such a configuration, the output of the power amplifier (power amplifier) 17 of the transmission unit 4 is determined in the time slot assigned by the base station, for example, as the waveform shown in FIG. It is increased at a given timing and decreased after a specified time. FIG. 6 shows allocation of time slots used in wireless communication between a base station and one mobile station in the case of the quadruple TDMA method, and at positions having the same slot number (slot number 1 in FIG. 6 is used). In (), wireless communication is performed between the base station and the same mobile station. The up period is a communication period from the mobile station to the base station, and the down period is a communication period from the base station to the mobile station.

As shown in FIG. 7, the data format in the dedicated cell channel which is one of the control channels as the format of the downlink slot data is, as shown in FIG. 7, the transient response ramp time (R) and the synchronization preamble (PR). ), Sync word (unique word: U
W), channel type (CI), destination identification code (DA) which is the calling code of the partner station, calling identification code (OA) which is the calling code of the local station, delay amount (N), control data such as link channel allocation , And error detection additional information (CRC). Similarly, as the format of the downlink slot data, the format in the communication channel is, as shown in FIG. 8, a transient response ramp time (R), a synchronization preamble (PR), a synchronization word (unique word: UW) in order from the slot head. ), Channel type (CI), error information T, communication data, and error detection additional information (CR)
C). An 8-bit guard time is placed between adjacent slots.

FIG. 9 shows the operation until communication is performed. When a call is received or a call is made, a transmission signal including control data of a link establishment request is transmitted from the antenna 1 by operating the keyboard 20 in the mobile station. In response to a link channel establishment request from the mobile station to the base station on the control channel, the base station may transmit a transmission signal including control data of a link establishment response from the antenna 1 to perform link channel allocation to the mobile station. Done. After switching to the communication channel by the link establishment response, the operation is performed by supplying the synchronization burst from the mobile station to the base station, the synchronization burst from the base station to the mobile station, and the communication mode setting request from the mobile station to the base station. Supply, response to communication mode setting from base station, supply of call setting request from mobile station to base station, response to call setting from base station,
After a function / authentication request is supplied from the base station to the mobile station, a response to the function / authentication request from the mobile station, a call from the base station to the mobile station, and a response, a call is made. These are transmitted as data in slots.

The arrival time of the slot data of the link channel establishment request is measured in the channel coding logic circuit 12 as the number of bits from the slot start reference time (when the slot start pulse is generated) in the delay amount measuring circuit,
Let the measurement time be the delay amount N. That is, C of the base station
The PU 19 reads from the output of the delay amount measuring circuit (count value of the counter 34) and subtracts the number of bits of the transient response ramp time (R), the synchronization preamplifier (PR) and the synchronization word (UW) from the count value. The delay amount N is set by. Then, the set delay amount N is included in the slot data for link channel allocation as shown in FIG. 7 to notify the mobile station.

The CPU 19 of the mobile station reads the delay amount N in the received data, presets the value MN corresponding to the delay amount N in the down counter 41, and supplies the shift start pulse to the down counter 41. As described above, the shift start pulse is generated by M bits (M clock cycles) earlier than the slot start pulse indicating the slot data transmission start time when the delay amount is not taken into consideration. Therefore, N bits are generated before the slot start pulse is generated. The clock pulse is supplied from the down counter 41 to the shift register 43 as soon as possible. Therefore, the transmission start time point of the slot data output from the shift register 43 is advanced by being advanced by the delay amount N (that is, the clock period of N bits), and the DSP 11 is responsive to the accelerated slot data output to cause the transmitting unit 4 to output. To control the slot data transmission state. Therefore, after shifting to the communication channel, transmission of each slot data from the mobile station to the base station is started earlier by N clock cycles.

As described above, during communication in the communication channel in which the transmission start timing of the slot data from the mobile station is advanced, the CPU 19 of the base station obtains based on the count value of the counter 34 as shown in FIG. It is determined whether or not the delay amount N is 0 (step S1), and N =
If it is 0, the reception timing of the slot data at the base station coincides with the reference timing, so the T value in the slot data to be transmitted next is inverted (step S
2). On the other hand, if N ≠ 0, the slot data reception timing at the base station does not coincide with the reference timing, so it is determined whether or not the delay amount N is positive (step S3). If N> 0, the slot data transmission start carry amount in the mobile station is small, so the error information T is made equal to 1 in order to increase the carry amount (step S4). N
If <0, the carry amount of the slot data transmission in the mobile station is too large, so the error information T is made equal to 0 to reduce the carry amount (step S5). Base station C
The PU 19 commands the channel coding logic circuit 12 to use the error information T thus determined in the downlink slot data in the next communication channel (step S6). Therefore, the error information T is transmitted in the data format shown in FIG. 8 in the slot in which the next base station transmits to the mobile station.

The CPU 19 of the mobile station judges whether or not the error information T read from the slot data of the communication channel has changed from the value of the error information T in the previous slot data as shown in FIG. It is determined from the output value of the circuit (step S11). If the value of the error information T has changed, the slot data transmission start carry amount is appropriate, so the current slot data transmission start carry amount is maintained.
However, if the value of the error information T has not changed, it is determined whether or not the error information T is 1 (step S1).
2). When T = 1, the preset value of the down counter 41 is decreased by 1 to increase the slot data transmission start carry amount (step S13). When the preset value is decreased by 1, the time from the generation of the shift start pulse until the count value of the down counter 41 reaches 0 is shortened, and the timing at which the clock pulse is supplied to the shift register 43 is 1 bit longer than before. It becomes faster by a minute (one clock cycle). Therefore, the timing at which the data is output from the shift register 43 is advanced by 1 bit, and the transmission start time of the slot data output from the shift register 43 is advanced by 1 bit, which is earlier, and the DSP 11 Further, the transmitting unit 4 is controlled in accordance with the slot data output which is advanced by one bit to bring the slot data into the transmission state.

On the other hand, when T = 0, the down counter 41 is used to reduce the carry amount of the slot data transmission start.
Increment the preset value of (step S1
4). When the preset value is increased by 1, the time from the generation of the shift start pulse until the count value of the down counter 41 reaches 0 becomes longer, and the timing at which the clock pulse is supplied to the shift register 43 is 1 bit longer than before. It will be delayed by a minute. Therefore, the timing at which the data is output from the shift register 43 is delayed by one bit, which delays the transmission start time of the slot data output from the shift register 43 by one bit, and the DSP 11 adjusts the delay by one bit. The transmitting unit 4 is controlled according to the output of the slot data, and the slot data is transmitted.

[0022]

As described above, in the signal arrival time correction method in the mobile communication system of the present invention, the base station determines the arrival time of the transmission signal every time it receives the transmission signal from the mobile station in the communication channel. The delay amount from the reference start time of the time slot is measured, the error information signal according to the measured delay amount is included in the transmission signal and transmitted to the mobile station, and the mobile station receives the error from the received transmission signal from the base station. Since the information is extracted and the transmission start timing for a predetermined time slot is adjusted according to the extracted error information, it is not necessary to provide a long guard time between each time slot, and the utilization efficiency of frequency resources can be improved. Can be higher. Further, since it is not necessary to use a complicated synchronizing circuit, the reference start time of each time slot in the base station and the arrival time of the transmission signal from each mobile station can be matched at low cost.

[Brief description of drawings]

FIG. 1 is a block diagram showing a wireless device to which a signal arrival time correction method of the present invention is applied.

FIG. 2 is a block diagram showing a configuration of a delay amount measuring circuit.

FIG. 3 is a block diagram showing a configuration of a time slot format generation circuit.

FIG. 4 is a block diagram showing a configuration of a T value determination circuit.

FIG. 5 is a diagram showing a change in transmission power in a time slot.

FIG. 6 is a diagram showing time slot allocation in the case of a quadruple TDMA method.

FIG. 7 is a diagram showing a data format in an individual cell channel.

FIG. 8 is a diagram showing a data format in a communication channel.

FIG. 9 is a diagram showing a control sequence until a call is made.

FIG. 10 is a flowchart showing the operation of the CPU of the base station.

FIG. 11 is a flowchart showing the operation of the CPU of the mobile station.

[Explanation of symbols for main parts]

 1 Antenna 3 Receiver 4 Transmitter 11 DSP 12 Channel Coding Logic Circuit 19 CPU 21 Voice CODEC 22 Data Input / Output Interface

Claims (7)

[Claims] 1. A base of a transmission signal for a predetermined time slot transmitted from a mobile station in a mobile communication system using a time division multiplex connection method in which a mobile station and a base station wirelessly communicate with each other in a predetermined time slot. A signal arrival time correction method for correcting an arrival time at a station, wherein a base station receives a transmission signal from a mobile station in a communication channel from a reference start time of the predetermined time slot of the arrival time of the transmission signal. The amount of delay is measured and the error information signal corresponding to the measured amount of delay is included in the transmission signal and transmitted to the mobile station.The mobile station receives the error information signal from the received transmission signals from the base station. Signal arrival time correction by extracting and adjusting the transmission start timing for the predetermined time slot according to the extracted error information signal Law. 2. The base station measures, in the base station, the delay amount from the reference start time of the predetermined time slot of the arrival time of the transmission signal of the link channel establishment request from the mobile station in the control channel, The data including the delay amount is transmitted from the base station to the mobile station together with the link channel allocation notification for the establishment request, and the mobile station advances the time corresponding to the received delay amount by the predetermined transmission start timing in the communication channel. 2. The signal arrival time correction method according to claim 1, wherein the time slot is transmitted. 3. The base station sets the level of the error information signal to a first level when the measured delay amount is a delay time of an arrival time.
When the measured delay amount is set to a predetermined value, the level of the error information signal is set to a second predetermined value when the measured delay amount is the advance time of the arrival time, and when the measured delay amount is 0, the first value is set.
The error information signal is set so that a predetermined value and the second predetermined value are alternately transmitted, and the mobile station sets the level of the error information signal extracted this time and the level of the error information signal previously extracted to the above-mentioned level. When it is the first predetermined value, the transmission start timing is advanced by a predetermined unit time, and the level of the error information signal extracted this time and the level of the error information signal previously extracted are both the second predetermined value. Delays the transmission start timing by the predetermined unit time,
When the level of the error information signal extracted this time and the level of the error information signal extracted last time are different from each other, the transmission start timing is maintained as it was when the level of the error information signal was extracted last time. Item 1. The signal arrival time correction method according to item 1. 4. The signal arrival time correction method according to claim 1, wherein the error information signal is a 1-bit data signal. 5. The signal arrival time correction method according to claim 3, wherein the predetermined unit time corresponds to a data transmission interval of 1 bit. 6. The signal arrival time correction method according to claim 1, wherein the base station measures the delay amount from the arrival time of the unique word in the transmission signal. 7. The mobile station has a preset down counter, the preset down counter is preset with a value according to the delay amount, and the preset value is increased or decreased according to the level of the error information signal, The preset down counter starts down counting in response to a shift start pulse determined in the mobile station at the time of occurrence for the predetermined time slot, and when the count value reaches 0, the mobile station starts transmission. The signal arrival time correction method according to claim 1 or 2, characterized in that.